Definition

Noun: A protective, insulating layer that surrounds and encases the axons of many nerve cells (neurons). It is composed primarily of a fatty substance called myelin and serves to increase the speed at which electrical impulses (nerve signals) travel along the axon.

Usage

The term is used in biological, medical, and anatomical contexts to describe the specific structure insulating nerve fibers. * It functions as a subject or object in a sentence. * It is often modified by adjectives or possessive forms to specify its condition or location.

Examples

• The myelin sheath is essential for the rapid conduction of neural signals.
• Damage to the myelin sheath, as seen in multiple sclerosis, can severely impair nerve function.
• Researchers are studying ways to promote the regeneration of the myelin sheath after injury.

Advanced Usage

• "Demyelination": The process of damage or loss of the myelin sheath.
  • Demyelination of the central nervous system is a hallmark of several neurological diseases.
• "Myelination": The process of forming a myelin sheath around an axon.
  • The myelination of nerve fibers continues throughout childhood and adolescence.

Variants and Related Words

• Myelin (noun): The fatty, insulating substance that forms the sheath itself.
• Myelinated (adjective): Describing a nerve fiber that is encased in a myelin sheath.
  • Myelinated axons appear white, forming the brain's "white matter."
• Unmyelinated (adjective): Describing a nerve fiber that lacks a myelin sheath.

Synonyms

• Medullary sheath (a less common, more technical synonym)
• Nerve insulation (a descriptive, non-technical phrase)

Related Phrases

• Saltatory conduction: The mode of rapid signal propagation in myelinated axons, where the impulse "jumps" between gaps in the sheath called Nodes of Ranvier.
  • The myelin sheath enables saltatory conduction, which conserves energy for the neuron.

Noun

1. a layer of myelin encasing (and insulating) the axons of medullated nerve fibers